Field of the Invention
The present invention relates to a heat dissipating device having an increased heat dissipating capacity, a light source unit including this heat dissipating device, and a projector including this light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen of a personal computer and a video image, as well as images based on image data which is stored on a memory card or the like on to a screen. In these data projectors, light emitted from a light source is collected to a micromirror display device called a DMD (Digital micromirror Device) or a liquid crystal panel for displaying a color image on to the screen.
Some of those projectors employ semiconductor light emitting elements such as laser diodes or LEDs as a light source. For example, a projector disclosed in Japanese Unexamined Patent Publication No. 2013-196946 includes an excitation light shining device including a plurality of semiconductor light emitting elements and a luminescent plate device on which excitation light is shone from the excitation light shining device to thereby emit luminous light. Then, a heat sink as a heat dissipating device for cooling the plurality of semiconductor light emitting elements of the excitation light shining device is provided on a rear surface of a holder which holds the plurality of semiconductor light emitting elements.
Additionally, Japanese Unexamined Patent Publication No. 2014-206581 discloses a projector which includes an excitation light source including laser diodes or the like and a luminescent plate. In this projector, a heat sink as a heat dissipating device is provided on a rear surface side of the excitation light source to cool the excitation light source, and a cooling fan is also provided to cool the heat sink. In this projector, the output of excitation light from the excitation light source is controlled according to the luminance level of a picture signal, and the output of cooling air from the cooling fan is also controlled.
The heat dissipating device such as a heat sink is provided for the light source which includes the plurality of semiconductor light emitting elements, as described above. This heat dissipating device can improve the heat dissipating efficiency by controlling the light source and the cooling fan. However, there exists an upper limit for the heat dissipating capacity. On the other hand, in these days, small and highly bright semiconductor light emitting elements are developed. Then, in a light source employing the plurality of such a small and highly bright semiconductor light emitting element, the heat generation density becomes high, and this makes it difficult for the semiconductor light emitting elements to be cooled, thereby making it difficult to realize a reduction in size of the light source, which would otherwise become possible by increasing the density of layout of the semiconductor light emitting elements. Then, the semiconductor light emitting elements and the holder which holds them cannot be formed small, thereby making it difficult to reduce the size of the projector.